Enabled EXT_sRGB WebGL extension support in the command buffer.

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 1213e616f2e1638adbfe653b2200607b04e69860..95061a6889b2840489d23ba51d33b00766715ac5 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -10089,6 +10089,8 @@ static GLenum ExtractFormatFromStorageFormat(GLenum internalformat) {
       return GL_LUMINANCE_ALPHA;
     case GL_BGRA8_EXT:
       return GL_BGRA_EXT;
+    case GL_SRGB8_ALPHA8_EXT:
+      return GL_SRGB_ALPHA_EXT;
     default:
       return GL_NONE;
   }